Imported Stp>expolde>Join>all one polysurf except one surface

hello all,

Im new to Rhino, but ive been recently using it to help smooth out surfaces I created in Solidworks.
Once i create the model (Solid) in SW I save as an STP and bring that into rhino. I need to explode the surfaces to delete the base surface of the model then rejoin them. But when i rejoin them, there is one surface which will not join back. It is shown as a surface where the others are shown as a polysurface’s. I have no clue why this is and its quite annoying.
If anyone has any ideas as to why this is happening, it would be much appricated.

FYI I tried saving the SW file as a surface by deleting the face i dont want and then importing this to rhino, but i still get the same issue. :frowning:

Hi Henry - please post an example here (public) or send to tech@mcneel.com, with a link back here in your comments.

-Pascal

Hi Pascal,

Thanks for getting back to me. here is a screen shot of the situation. and the file in questions attached.
Cheers
Surface Issue 1.3dm (1.8 MB)

Hi Henry - the surfaces are definitely well out of tolerance (0.00001, pretty tight) Is the new surface the strip in the middle? Can you send me, via tech@mcneel.com, the original you are working with in Rhino, the step file, maybe there is something I can figure out that will help, workflow wise.

-Pascal